I have a business object mapped to a single table Table1. In FillDataTable the query retrieves few extra columns from Table2 by joining Table1 and Table2. How do I map columns from Table2 to a GridView in a webform?

What you'll need to do is add a new property to the main code file (not the .designer.* file since it could be overwritten) by copying one of the properties from the .designer.* file and modify it accordingly.  Then, you'll need to override the GetCustomBindablePropertyDescriptors() method to return the property descriptors for the properties that you added.  If you search the forum for "GetCustomBindablePropertyDescriptors" you'll find several articles on both custom properties and how to override that method.

Thank you! That helped.